Markayendeyulu G

The structural and magnetic properties of Nd3 (Fe1-x Alx) 27.5 Ti1.5 (x=0.1-0.4) were investigated by x-ray diffraction, magnetization, and Curie temperature (TC) measurements. The unit cell volume increases with the Al substitution, in accordance with the larger atomic radius of Al. The saturation magnetization and the Curie temperature decrease with increasing Al content, and the decrease is attributed to the modification of the density of states of 3d band due to the 3p band of Al and to the magnetic dilution effect. The easy direction of magnetization is along the b axis for x=0.4. The anisotropy field (HA) decreases with increasing Al concentration. © 2006 American Institute of Physics.

The effect of Al on the structural and magnetic properties of Pr3 (Fe1-x Alx) 27.5 Ti1.5 (x=0.1, 0.2, and 0.3) compounds has been investigated by x-ray-diffraction, magnetization, and Curie temperature measurements. All these compounds have formed in monoclinic symmetry with A2m space group with Pr(Fe,Ti) 12 as secondary phase and traces of α-Fe. The monotonic decreases in MS both at 300 and 80 K are discussed on the basis of electron transfer from the 3p band of Al to the 3d band of Fe near EF. The variations in TC are explained using the Friedel approach. In all the compounds, the easy magnetization direction is away from the b axis. © 2006 American Institute of Physics.

Ferromagnetic and ferroelectric characteristics of Gd substituted nickel ferrite (NiO Fe1.925 Gd0.075 O3) were investigated. The material formed in the cubic inverse spinel phase and in addition, a small amount of GdFe O3 phase was identified. A small distortion of the cubic lattice was observed upon the substitution of Fe by Gd in the B site. Substitution of Gd for Fe lowered the saturation magnetization. However, the saturation magnetostriction is seen not to change significantly by the substitution of Gd. From the temperature variation of dielectric constant measurement, the ferroelectric transition temperature was found to be 512 K. The existence of the ferroelectricity was confirmed from the ferroelectric loop. The (high) dielectric constant with frequency is seen to reveal a dispersion of relaxation times. © 2008 American Institute of Physics.

Magnetoresistance (Δρ ρ) studies have been carried out on the C15-type cubic Laves phase Ho0.85Tb0.15Mn2-xFex (x=0, 0.25, 0.5, 1, and 2) compounds up to a magnetic field of 90kOe at temperatures 5, 30, and 100K. The lattice parameters were found to decrease with increasing x. The Curie temperature is found to increase with increasing x from 30to680K, which is attributed to the net increase in the exchange splitting of the spin-up and spin-down bands. A maximum value of Δρ ρ of -27% was observed for Ho0.85Tb0.15Mn2 around the ordering temperature. This is explained on the basis of nearest Mn-Mn critical distance. A positive magnetoresistance, increasing in a discontinuous manner with increasing field, due to the dependence of scattering of conduction electrons on large magnetoelastic interactions, was observed at 5K in Ho0.85Tb0.15Fe2. © 2005 The American Physical Society.

The structural and magnetic properties of YGdFe17_xCox Ga (x = 0,1, 2 and 3) have been investigated through X-ray diffraction and magnetization studies. All the compounds up to x = 0.2 are formed in a single-phase, hexagonal structure. The unit cell volume decreased with the addition of Co due to the smaller size of Co than that of Fe. The magnetization and Curie-temperature values are found to increase with the addition of x and could be due to the additional Co-Co, Fe-Co exchange whose magnitude is larger compared to that of Fe-Fe exchange. Magnetically aligned sample powders indicate the presence of planar anisotropy for all the compounds. © 2006 IEEE

It had been reported that B has beneficial effects on the magnetostriction of anisotropy compensated Dy0.7 Tb0.3 Fe2 alloys. In the present work, Dy0.7 Tb0.3 Fe1.95 and Dy0.7 Tb0.3 Fe1.95 Bx (x=0.1, 0.15, and 0.2) alloys, in the form of 8 mm diameter cylindrical rods, were investigated both in the as-cast and zoned conditions. At 5 kOe dc magnetic field, magnetostriction of ∼1200 and 900 microstrains was observed for zoned samples with x=0 and 0.1, respectively. For zoned samples with x<0.1 and for the as-cast sample of the parent alloy, magnetostriction of ∼500 microstrains was measured. X-ray diffraction of the zoned x=0 and x=0.1 samples showed a strong prevalence of the 〈112〉 and the 〈110〉 grain orientations; in contrast, the other samples appeared to possess a random grain orientation. Optical and scanning electron microscopy studies revealed a significant increase in the volume fraction of the R Fe3 phase with increasing boron content. This increase in the volume fraction of the (Tb,Dy) Fe3 phase and the reduction in the desired grain orientation of the (Tb,Dy) Fe2 phase are attributed to be the reasons for the large decrease in the magnetostriction of the (Tb,Dy) Fe1.95 alloys with boron addition. © 2007 American Institute of Physics.

The electrical and Hall resistivities of Tbx Fe100-x thin films in the temperature range 13-300 K were investigated. The sign of Hall resistivity at 300 K is found to change from positive for x=28 film to negative for x=30 film, in accordance with the compensation of Tb and Fe moments. All the films are seen to have planar magnetic anisotropy at 13 K. The temperature coefficients of electrical resistivities of the amorphous films with 19≤x≤51 are seen to be negative. The temperature dependence of Hall resistivity of these films is explained on the basis of random magnetic anisotropy model. The temperature dependences of Hall resistivities of the x=22 and 41 films are seen to exhibit a nonmonotonous behavior due to change in anisotropy from perpendicular to planar. The same behavior is considered for the explanation regarding the probable formation of Berry phase curvature in these films. © 2009 American Institute of Physics.

The structural, electrical and magnetic properties of Ho 0.85Tb0.15Fe2Bx (x = 0,0.05,0.1,0.15) have been carried out through X-ray diffraction, electrical resistivity and magnetization measurements. All the alloys are found to crystallize in C15-type cubic Laves phase structure. It is observed that the lattice parameter is found to increase with increasing boron concentration, which may be due to the occupation of boron at interstitial sites. The magnetization and Curie temperature are found to be constant with the increase in x. The temperature variation of electrical resistivity shows a metallic behavior with an increase in resistivity with increasing boron concentration. The resitivity behavior is explained on the basis of electron-magnon scattering at low temperatures and electron-phonon scattering at high temperatures. © 2004 Elsevier B.V. All rights reserved.